Having taken my front wheels of for balancing (damn left handed threads) I noticed my front drums are mis-matched the drivers side is mor square with a spring around the outside, while the passenger side is a little more rounded with no spring.

What does that spring do? I took the wheels off to get balanced because I had a vibration on the front passenger side wheel while at highway speeds 120kph, the vibration starts at 120 and there is no sign of it before that speed, and no sign or indication of an alignment problem, had an alignment done last year and haven't driven 200km since.

Hope the pictures show the difference in the two drums.

 

The different drums are not bad, but a sign of someone that was cheap with maintenance. Both wheels have traveled the same distance and should be replaced at the same time. If there was accident damage to one side of the vehicle the insurance would have only paid to replace that side. Often a brake will stick on one side causing that drum to wear faster than the other side and the owner will replace just one rather than both. Not horrible but not right either. If they are not out of spec you could leave it like that but I would change them both, start fresh and even. The spring has been attributed to a couple things: 1. Harmonics. removing vibration noise. 2. Heat sink. This gives more contact area for the drum to cool faster. If the new drums dont have the spring (and they likely wont) It doesn't matter.

 

My 67 has the springs on the front drums and none on the back. ~shrugs~